Process of wet spinning stereoregular polyvinyl alcohol



Sept. 3, 1963 N. v. SEEGER 3,102,775

PROCESS OF WET SPINNING STEREOREGULAR POLYVINYL ALCOHOL Filed June 17, 1960 WIN!) UP DRYER RPVA SOLVENT INVENTOR NELSON V. SEEGER ml mclwu ATTORNEYS United States Patent 3,102,775 PROCESS OF WET SPINNING STEREOREGULAR POLYVINYL ALCOHOL Nelson V. Seeger, Painesville, Ohio, assignor to Diamond Alkali Company, Cleveland, Ohio, a corporation of Delaware Filed June 17, 1960, Ser. No. 36,738 5 Claims. (Cl. 18-54) This invention relates to the production of films, fibers, threads, filaments and similar articles. More particularly, it relates to the production of such articles from polyvinyl alcohol.

It is known that polyvinyl alcohol, which is soluble in water, can be spun into fibers by wet or dry spinning methods from an aqueous solution of the resin. Such fibers, however, are characterized by their sensitivity to water, particularly to hot Water. If dipped in water at normal temperature, the fiber will shrink by more than of its original length, and if the temperature of the water is around 7090 C., the fiber will dissolve.

Polyvinyl alcohol (PVA) fibers have been made resistant to water by various methods including modification of the alcohol prior to spinning and by after-treatment of the fiber. It has been known to incorporate into the polyvinyl alcohol spinning solution a compound such as a dicarboxylic acid which is capable of forming a crosslinked structure under the influence of heat. It has also been been known to acetalize the polyvinyl alcohol, then form a fiber and follow up with a heat treatment of the fiber.

Fibers, after being spun from a PVA solution, have been made resistant to water by various treatments such a stretching and heat-treating, stretching and reacting with a material such as an aldehyde, ketone or dibasic acid, exposure to formaldehyde vapors or elevated temperatures and treatment of the fiber surface with waxes, etc. Such treatments are expensive and often introduce undesirable physical characteristics and impurities in the treated fibers.

As with other types of synthetic fibers, a moderate amount of drawing or stretching orients the molecular structure and results in high tensile strength. This orientational drawing, however, is distinguished from the stretching which accompanies the aforementioned insolubilizing treatments.

This invention has as an object an oriented high-tensity polyvinyl alcohol fiber which, without the well-known in- ,solubilizin'g treatments, is insoluble in boiling water. A

further object is 'a method of preparing such fibers from polyvinyl alcohol resins which are substantially insoluble in boiling water. Other objects will be obvious from a careful study of the following description of this invention.

Conventional polyvinyl alcohol is obtained by saponification, hydrolysis or alcoholysis of polymerized vinyl esters, especially vinyl acetate. The molecular weight of the polyvinyl alcohol is dependent upon that of the ester, i.e., a high molecular weight polyvinyl alcohol is obtainable from an ester having a correspondingly high molecular Weight. The conventional polyvinyl alcohol having a reduced viscosity of 1.0 is completely soluble in water at a temperature of about C. Accordingly, an aqueous solution of polyvinyl alcohol may be employed to produce fibers, films, etc. therefrom.

The polyvinyl alcohol of this invention, hereafter referred to a stereoregular polyvinyl alcohol or RPVA, is obtained by alcoholysis of polymerized vinyl halo esters, especially vinyl chloroacetates and vinyl fiuoroacetates, as disclosed in US. patent application Ser. No. 689,768, filed October 14, 1957, and now Patent No. 2,901,341. The stereoregular polyvinyl alcohol having ,a reduced viscosity of 1.1 will not dissolve in water at a temperature of C. RPVA may be dissolved in water at a temperature of 1l5-120 C. The insolubility of stereoregular polyvinyl alcohol in water at 100 C. has been attributed to the syndiotacticity of the alcohol as contrasted to an atactic structure possessed by conventional polyvinyl alcohol.

Since pressurized equipment is necessary to maintain a water temperature in the neighborhood of C., it may be desirable to employ an organic solvent to form the spinning solution. Stereoregular polyvinyl alcohol is not only insoluble in boiling water but is also insoluble in most solvents or combinations thereof. In order to determine the eliect of various solvents on RPVA, a film of the material was cast from a water dispersion of the resin. The dispersion was spread on a glass plate and the water evaporated therefrom to form :a film. Small sections of this film were immersed in the solvents tested and the effect of numerous solvents is shown in Table I.

TABLE I Reagent After 5 hrs. at room temp. After 24 hrs. at room temp. Additional 5l1rs. at 50-55C. Additi0nal2 hrs. at 9095C.

Water NNE NNE- NNE NNE. Ethylene diamine dissolved dissolveddissolved, Acetic acid, glaciaL NE NNE. N NE v. sl. swolle1 Acetic anhydride NNE N E NNE. Ammonium thlocyanate (sat. $01.). considerable swelling consid considerable swelling Formic acid (98100%) "-410 -d degradation. Lthium bromide (607 sol.) d0 -419 greatly swollen. Zinc chloride (60% s0l.).. considerable swelling. considerable swelling. dissolvechpink, Ethylene chloriclc NNE 50 C NNE 50 C. NNE. Propylene carbonate NN N NE NNE 2-nitropropane- N NE. Butyrolactone N N E. Tetrahydrofurluryl ale NN E. Chloromaleic anhydridc NNE. Triethylenc diamine (sat. sol apparently dissolved. Morpholine v. s1. swollen. N-methy1 degradation v. v. s1. swollcn. Piperidine swollen. Pyridine N NIB-darkened. Piperazine (sat. sol.) appears to be dissolved. Triethanolamine NNE N NE. Diethanolamine NN E N itroethanc NNE. Acetonitrile NN E N-acetylmorpholine N N E 1, 6-hexanediamine-7 Resorcinol (set. 501).. Capmlaetam (sat. s01.) Dimethyl sulfone (sat. so Dimethyl sulfoxide Tricresyl phosphate See footnotes at end of table.

sl. swollen considerable swelling NN appears to be dissolved consderable swelling 0 swollen considerable swelling N N E Reagent at room temp. After 24 hrs. at room temp. Additional hrs. at 50-55C. AdditionalZ hrs. at 90-95%? chloroform NNE.. NNE. NN E. Sanoticizer' 1'41 N N E- N NE. Diacetin--. NNE.-- NNE. Formamidesl. swollen sl. swollen Triisoootyl phosphi'te NN E NE. bisgf-ethylhexyl) hydrogen phos- NNE N NE.

p ate. fi-hydroxypropi'onitrile NN E. swollen. 2(2-an1inoethylamine) ethanol appears to be dissolved... appears to be dissolved. z-pyrrol one v. sl. swollen greatly swollen. N-metliylacetamide NN sl. swollen. Propargyl alcohoL. v. sl. swollen V. sl. swollen. Shell Curing Agent T- NNE N NE. Diglyme... NNE-. NNE Tetramethylene sulfone N N E. NNE. fl-alanine (sat. sol.) sl. swollen swollen. Glycine (sat. sol.) sw0llen. swollen o. Guanylurea phosphate (sat. sol) 0 -do. greatly swollen greatly swollen. Methylamine sol.) appears to be dissolved-. appears to appears to be dissolved.-- appears to be dissolved. Methane diam NNE.- NNE. NNE. B-hydroxyethyl trimethyl ammonv. sl. swollen v. sl. sw ll n sl. swollen swollen.

ium-bicarbonate%. Cyanamide (sat. sol.) considerable swelling considerable swelling. greatly swollen dissolved.

NNE NNE E sl. swollen.

fl-propiolactone Urea (sat. sol.) Onyx ETC-%- Nrnon (c ono) SO2/dimethyl formamide, saturated NN SOz/tetrahydrofuran, satnrated..-" LiBr/dimethyl formamide, saturated. LiBr/dimethyl sulioxide, saturated- LlBr/tetrahydrofuran, saturated-... ZnClgldimethyl formamide, saturated. ZnOlz/d'imethyl sulfoxide, saturated Zn clzltetrahydrofurzin '1 in m fed greatly swollen considerable swelling v.v.sl. swollen Dimethyl fOrmamide/HZO, 4:1

ratio. Dimethyl sulioxide/HzO, 4:1 ratio.- PhD/ethylene glycol, 4:1 ratio Triton /H2O, (conc. 501.)- Diacetone alcohol Tetrahydropyran-Z-methanol Ethyl carbamate.- Ethylene glycol Urea/tetrahydroinran, saturated.... Urea/dimethyl formamide, saturated. Urea/ethylene glycol, satnrated.. N

Urea/dimethyl sulfoxide, saturated.

Ureal2-pyrrolidone NNE Cyanarnide/tetrahydrofuran, saturated.

Oyanamide/dimethyl iormarnide,

saturated.

Cyananiide/ethylene glycol, saturated.

Cyanamide/dimethyl sulfoxide,

saturated.

Triethylene diannne/tetrahydrofuran.

Triethylene diarnine/dimethyl formamide. Triethylene diamine/ethylene glycol. Triethylene diamine/dimethyl sulfoxide. Triethylene diamine/Z-pyrrolidone. Caprolactam/tetrahydroiuran Caprolactam/dimethyl formamide. Caprolactam/ethylene glycol Piperazine (hydrate)/tetrahydrofuran. Piperazine(hydrate)/dimethylforn1- ami e. Pipelrazine(hydrate)/etl1ylene glyeo Piperlzinewydratefldimethyl sulfex e. Guanylurea phosphate/tetrahydrofuran.

Guanylurea phosphate/dimethyl formamide.

Guanylurea phosphate/ethylene glycol.

Guanylnrea phosphate/dimethyl sulfoxide.

Dichloroacetic acid/glycerine Dichloroacetic acid/tetrahydrofuran.

Dichloroacetic acid/dimethyl formamide.

Dichloroacetio acid/dimethyl sulfoxide.

v.v.sl. swollen greatly swollen greatly swolle considerable swellingconsiderable so dissolve dissolved swollen- .do

NNE NNE NNE greatly swolle sl. swollen extremely swollen- NNE NN NNE v. v. s1. swollen.

sl. swollen extremely swollen NNE. N NE.

51. swollen swollen v.v.sl. swollen extremely swollen N N o extremely swollen NN NNEI" NNE:

NNE v. v. sl. swollen NNE- NNE considerable swelling extremely swollen swollen considerable swelling considerable swelling NNE- NN E- NN E. sl. swollen NNE v sl swollen..

sl.swo1len considerable swelling considerable swellin NNE N N E. NNF NNE. NNE. sl. swollen NN E- NE. NNE sl. gel. in.

NNE NNE NNE NNE N NF sl.swollen considerable swelling considerable swelling NN E N NE.

NNE NNE-.. sl. swol NNE. do

swollen considerable swelling considerable swelling NNE N N E N N E N N E. NNE

NNE- v. sl. swollen extremely swollen N NF NNE- Triethylamine- NNE NNE. Duponol WA/HzO considerable swelling considerable swelling considerable swelling dissolved (may contain gel) considerable swelling.

NNE.

greatly swollen. extremely swollen. NNE.

partially dissolved.

( extremely swollen.

greatly swollen. extremely swollen. N E.

swollen.

sl. swollen.

swollen.

g tglelgnlely swollen.

v. v. sl. swollen.

swollen.

considerable swelling.

sl. swollen.

swollen.

considerable swelling.

extremely swollen.

swollen.

sl. swollen.

N N E.

swollen.

dissolved.

sl. swollen.

swollen.

considerable swelling.

v. sl. swollen.

sl. swollen.

extremely swollen.

considerable swelling. N N E considerable swelling.

*Alkyl (Ca-Q15) dimethyl benzyl ammonium chloride-25% sol.

From Table I it will be noted that ethylene diamine, saturated solution of triethylene diamine, saturated solution of piperazine, 72% solution of 1,6-hexanediamine, 30% solution of methylainine and concentrated hydrochloric acid apparently dissolve the stereoregular polyvinyl alcohol. The aqueous solutions of triethylene diamine, piperazine, hexanediarnine and methylamine all are quite alkaline, having a pH in the neighborhood of about 12. Films of RPVA which were reprecipitated from these solutions were found to be water-soluble and this led to the belief that such materials cause a possible degradation of the alcohol, accounting for its solubility. Concentrated HCl is very difficult to handle and therefore is undesirable :as a solvent. For preliminary work, ethylene diamine was selected as the solvent in the preparation of the spinning solutions.

The use of a solvent other than water to form the spinning solution resuires that the coagulating bath consist of a material in which the solvent is soluble and the polyvinyl alcohol is insoluble so that the solvent may be extracted from the fiber. When ethylene diamine is used as the solvent, the coagulating hath may consist of an anhydrous alcohol, e.g., methanol at room temperature. If the solvent employed is a 33 /3% aqueous solution of urea, hot methanol, i.e., at a temperature of about 4040 C., has been found to be the most effective coagulating medium. Fibers of stereoregular polyvinyl alcohol may also be produced from an aqueous solution provided the system is pressurized so that the temperature of the spinning solution may be maintained at about 120 C. If the pressurized, aqueous solution is employed, the fibers may be dry-spun into a high humidity atmosphere or a series of chambers of decreasing pressure so as to prevent the water from evaporating from the fiber too rapidly.

Typically, a solution of stereoregular polyvinyl alcohol in ethylene diamine is extruded by means of a gear pump through a multihole spinnerette into a coagulating bath of methanol or other lower aliphatic alcohol containing up to tour carbon atoms. From the coagulating bath the fiber or yarn is led to a positively-driven godet and then through air to a positively-driven wind-up bobbin. By adjusting the speeds of the various drives, the fiber can be stretched or drawn in controllable amounts either in the coagulating bath or in air between the godet and wind-up or both.

It has been found advantageous to provide a heatsetting operation following the drawing which comprises immersing the fiber or passing it through a hot mineral oil bath at a temperature of about 120 to 180 C. This heat-setting operation may be accompanied by a hotstretch operation whereby the fiber, while hot, is stretched 4 to 8 times its original length. The heat-setting and/ or hot-stretch is deemed necessary in order to provide insolubility in boiling water and a favorable tensile strength to fibers formed from stereoregular polyvinyl alcohol having a reduced viscosity in the neighborhood of about 0.4. Fibers formed from RPVA having a reduced viscosity or" 1.2 or higher are insoluble in boiling Water without being subjected to the heat-setting or hot-stretch operations. The stretching or drawing operation does, however, orient the fibers and greatly increases their tensile strength.

Fibers produced from water-insoluble stereoregular polyvinyl alcohol, in accordance with this invention, have a high tenacity and are insoluble in boiling water. Such fibers are important in industral uses such as cords for tires, fire hoses, industrial cords and belting, and in reinforcing fibers for many applications.

Reference has been made to the reduced viscosity (N of polyvinyl alcohol. This value is an indication of the molecular weight of the polymer and is equal to the specific viscosity (N divided by the concentration of polymer in the solution. The flow time of the polymer solution 1 and the flow time of the solvent t are usually measured by the capillary method. From these values the specific viscosity is computed according to the formula The reduced viscosity has a logarithmic relationship to the molecular weight of the polymer and, in general, the range is:

Approximate red' molecular weight .5 40,00060,000 1.0-1.5 100,000200,0O0 3.0 500,0001,000,000

Since conventional polyvinyl alcohol is soluble in water, water generally is used as the solvent in determining the reduced viscosity. Reduced viscosity of RPVA cannot be determined in this manner, however, since it is insoluble in water. Accordingly, the reduced viscosity of the precursor, i.e., polyvinyl chloroacetates or polyvinyl fiuoroacetates, is determined and, as is common practice in the polymer field, this value is assumed to be proportional to the reduced viscosity of the polyvinyl alcohol.

Denier of fibers is defined as the weight in grams of a 9,000-meter length of thread and is determined by measuring 9 meters of thread on a standard textile skeiner. The thread is removed from the skeiner and wound into a small loop about 1 inch in diameter. The loop of thread is agitated in isopropyl alcohol to remove any oil or other material which may be present on the thread surface and then air-dried. The weight of the loop in milligrams, as determined on an analytical balance, equals the denier of the sample.

Apparatus for determining tensile strength. and ultimate strength consists of a triple-beam laboratory scale. To one pan of the scale is attached a #25 chain which then loops over a sprocket and hand wheel near the level of the balance, such that turning the hand wheel adds more chain to the pan of the balance, thus gradually adding weight to that pan. The second pan of the balance has a drum-type fiber, clamp attached below it. Directly below this clamp is a second clamp mounted with a rack and pinion which, through a hand wheel, can raise or lower the clamp. In operating the apparatus, the chain and sliding weights on the balance are set at 0. The lower clamp is raised so that the clamps are 5 inches apart. The thread sample is clamped in the upper clamp and then pulled through the lower clamp to a point where the balance pointer reads 0 to insure that the sample is caught between clamps. The chain hand wheel is turned at a rate so as to add bout 1 gram per second to the load. At the same time the other hand wheel is turned to lower the clamp, thus keeping the balance pointer at the center mark. When the thread sample breaks, rotation of both hand wheels is stopped. At this point the sample is checked to ascertain whether the break occurred at the nip of the clamps and, if such is the case, that reading is discarded. Using the sliding weights of the balance, the weight of the chain is balanced and the reading on the scale is the breaking point. The distance the lower clamp has moved from its original position determines the ultimate stretch. The arithmetic mean of 10 breaking strength determinations is divided by the denier of the thread to give the grams per denier. The average of 10 ultimate stretch values, calculated as a percentage of 5 inches, gives the ultimate stretch percent.

Tenacity in grams per denier is converted to poun per square inch by the formula:

S G 1.24X 10 x (1 X wherein:

S= trength in pounds A =cr0ss sectional area of the fiiber in square inches d=density of the fiber in grams per cubic centimeter %=strength or tenacity in grams per denier The density of RPVA has been determined as 1.30 gr./cc. Substituting this value in the above formula, the tenacity in pounds per square inch is equal to 16,000Xgrams per denier The drawing illustrates the instant invention in the form of a flow sheet.

In order that those skilled in the art may more completely understand the present invention and the preferred methods by Wll'llCll the same may be carried into effect, the following specific examples are offered.

Example 1 A prototype laboratory spinning apparatus is employed which comprises a reservoir for the spinning solution which feeds two positive displacement metering pumps which are so interconnected and are run by variable speed motor so as to permit the accurate metering of as little as 3 l0- cc. per minute for the spinning solution. This apparatus is designed as a precision meter to extrude a uniform filament of spinning solution through the spinnerette orifice. A candle filter, using muslin as the filtering medium, is mounted in such a way as to permit the spinnerette to be raised from and lowered into the coagulating bath without interfering with the flow of spinning solution. The main purpose of the filter is to minimize the incidence of clogging of the spinnerette orifice. The spinneret-te is attached to the filter through a glass tube. The coagulating bath is contained in a stainless steel tray, 24 inches long, With an effective fiber immersion length of 18 inches. Single-stretching of the fiber is effected by wrapping the fiber once around a step on a step cone, then to a rewind spool. The diameters of the steps are calculated to permit any elongation from O to 1000% in 50% increments. Sequential stretching is effected by two step cones mounted parallel and rotating at the same speed. The fiber is fed around the two smallest diameter steps, then around successive larger steps and is finally wound on a rewind spool. The diameters of the steps vary from /2 inch to 4 inches and %-inch increments,

permitting up to 700% stretch by this method.

An ethylene diamine solution containing 24% stereo- A Example 2 A quantity of stereoregular polyvinyl alcohol resin having a reduced viscosity of 1.5 is dissolved in ethylene diamine to provide a solution of about solids. Using the apparatus of Example 1, this solution at room temperature is extruded through an eight-hole spinnerette at a rate of 1.5 feet per minute into a coagulating bath of absolute methanol. This fiber is then dried and is insoluble in boiling water.

Water resistance and dry tenacity'of various fibers are presented in Table II:

Water. The agitator is started .and an amount of RPVA, equal to 10% of the total mix, is slowly added directly into the vortex. The mixture is agitated for 30 minutes and then is heated to a temperature of 120C. under a pressure of 15 psi. The mixture is maintained at this temperature for about one hour, during which time all of the RPVA is dissolved. If the RPVA solution is to be used immediately, the pressure is removed and the solution may be cooled to a temperature of about C.

Example 4 An aqueous solution of water-insoluble RPVA having a reduced viscosity of 1.5, prepared as in Example 3, is employed to form water-insoluble fibers. Using a prototype laboratory spinning apparatus, the solution is spun through .a spinnerette containing eight orifices, each of which is 0.003 inch in diameter, into a chamber containing air having a high relative humidity. The strand is wetstretched 1.5 times and wound on a supply spool. The fiber, after being dried at room temperature, is insoluble in boiling water.

Example 5 *In a laboratory prototype spinning apparatus an aqueous urea solution containing 10% RPVA having a reduced viscosity of 1.5 is extruded by means of a gear 1 pump through a spinnerette at a rate of 1.5 feet per minute into a coagulating bath of absolute methanol having a temperature of 4070 C. The fiber passes through i the coagulating bath an effective distance of 18 inches,

providing a coagulation time of 60 seconds at this extrusion rate. The strand is wet-stretched 1.5 times, wound on a supply spool and dried at room temperature. The fiber thus produced is insoluble in water at 100 C.

It is to be understood that although the invention has been described with specific reference to particular embodiments thereof, it is not to be so limited, since changes and alterations therein may be made which are within the full intended scope of this invention as defined by the appended claims.

What is claimed is:

1. The method of producing stereoregular polyvinyl alcohol fibers which are insoluble in water at 100 C. comprising the steps of forming a solution of stereoregulair polyvinyl alcohol having a reduced viscosity of about 1.5 in a solvent selected from the group consisting of water under superatmospheric pressure, ethylene diamine and aqueous urea, extruding the solution through -a spinnerette into a coagulating medium selected from the group consisting of lower aliphatic alcohol and high humidity air, Wet stretching the fiber about one to three times its original length and drying the fiber at room temperature.

2. The method of producing stereoregular polyvinyl alcohol fibers insoluble in water at 100 C. which com I 9 10 prises the steps of forminga solution of stereoregular 5. The method of claim 2 wherein the coagulating polyvinyl alcohol in ethylene diamine containing about bathis absolute methanol.

3% to 24% by weight polyvinyl alcohol, extruding the solution through a spinnerette into a coagulating bath of References Clted the file of thls patent lower aliphatic alcohol containing up to 4 carbon atoms 5 UNITED STATES PATENTS and wet-stretching the fiber to about 1 to 3 times its 2,447,140 Shelton et al. Aug. 17, 1948 Original Iwgth- 2,517,694 Merion et :al Aug. 8, 1950 l 3. The method of claim 2 wherein the solution con- 2,610,360 Cline et al Sept. 16, 1952 tains about 10% polyvinyl alcohol. 2,610,359 Hatchand et a1. Sept. 16, 1952 4. The method of claim 2 wherein the polyvinyl a1- 10 2,642,333 Tomonari et al -1 June 16, 1953 cohol has a reduced viscosity of at least 1.5. 2,715,763 Marley Aug. 23, 1955 

1. THE METHOD OF PRODUCING STEREOREGULAR POLYVINYL ALCOHOL FIBERS WHICH ARE INSOLBUE IN WATER AT 100*C. COMPRISING THE STEPS OF FORMING A SOLUTION OF STEREOREGULAR POLYVINYL ALCOHOL HAVING A REDUCED VISCOSITY OF ABOUT 1.5 IN A SOLVENT SELECTED FROM THE GROUP CONSISTING OF WATER UNDER SUPERATMOSPHERIC PRESSURE, ETHYLENE DIAMINE AND AQUEOUS UREA, EXTRUDING THE SOLUTION THROUGH A SPINNERETTE INTO A COAGULATING MEDIUM SELECTED FROM THE GROUP CONSISTING OF LOWER ALIPHATIC ALCOHOL AND HIGH HUMIDITY AIR, WET STRETCHING THE FIBER ABOUT ONE TO THREE TIMES ITS ORIGINAL LENGTH AND DRYING THE FIBER AT ROOM TEMPERATURE. 